Good news! This issue has already been fixed! The 'X' button is now available on the Wildlife Rescue Tour.
Thank you for your continued support!
We have received reports that players are unable to close the Wildlife Rescue Tour screen because the "X" icon is missing. Not to worry! Our Team is already aware of this matter and is currently working on a fix.
For the meantime, you may close it by clicking on the 'Craft' button instead of refreshing your whole game. This will also ensure that all progress made on this feature, such as redeeming rewards, is saved successfully.